Recently, a surface state of an end portion of a substrate, e.g., a semiconductor wafer (hereinafter, simply referred to as “wafer”), is considered to be important in view of improving a production yield in the manufacture of semiconductor devices. While performing an etching process, a film forming process or the like on the wafer, undesired deposits may be adhered to the end portion of the wafer.
For example, when a plasma etching process is performed on a wafer surface by using a plasma of a fluorocarbon-based (CF-based) gas used as a processing gas, by-products (deposits) of fluorocarbon-based (CF-based) polymer are generated by competing reaction (polymerization reaction) to thereby be adhered not only to a device surface on the wafer but also to the end portion of the wafer (e.g., a rear side of the end portion which includes a beveled portion).
Further, when a CF-based film is formed on the wafer surface by employing a CVD (chemical vapor deposition) method by using a CF-based gas, the CF-based film extends from the wafer surface to the end portion. Moreover, it may extend further to the rear side of the end portion.    Patent Document 1: Japanese Patent Laid-open Application No. H5-102101    Patent Document 2: Japanese Patent Laid-open Application No. H10-242098
The deposits adhered to the end portion of the wafer are peeled off when the wafer is supported at the end portion thereof or is transferred, and then are adhered to the wafer surface, thereby decreasing a production yield of semiconductor devices to be manufactured. Therefore, the deposits adhered to the end portion of the wafer need to be removed by cleaning.
Conventionally, the deposits are used to be removed by polishing the end portion of the wafer by a brush or a tape. However, in the case of polishing the end portion of the wafer, it is troublesome to remove dust generated by the polishing and, also, contamination may be caused by the dust. Accordingly, the deposits adhered to the end portion of the wafer need to be removed without the polishing process.
Patent Document 1 discloses therein a method for removing fluorocarbon-based polymer on a wafer by applying ultraviolet to the wafer and simultaneously generating a plasma of nitrogen monoxide. In this method, however, a film (e.g., a low-k film) formed on the wafer may be damaged by the plasma thus generated, depending on the type of the film. Therefore, the deposits adhered to the end portion of the wafer need to be removed without inflicting damages on the wafer surface.
Moreover, Patent Document 2 discloses therein an apparatus including a supporting unit for rotatably supporting a wafer and an ultraviolet generation unit for applying ultraviolet to a part of a periphery of the wafer to thereby remove foreign substances adhered to the part of the periphery of the wafer (uneven part used for supporting the wafer). However, with this apparatus, the ultraviolet is applied only to a part of the periphery of the wafer. Therefore, in order to clean the entire periphery of the end portion of the wafer, the cleaning needs to be performed while the wafer being slightly rotated. As a consequence, a long period of time is required to remove the deposits. Furthermore, a rotation shaft of the supporting unit needs to coincide with a central portion of the wafer, or a position of the ultraviolet generation unit needs to be adjusted. As a result, required control processes increase.